The present invention relates generally to heat exchangers and more specifically to a return bend asembly for use in a multiple pass counterflow heat exchanger of the fin and tube type construction.
Heat exchangers of the fin and tube type construction are employed in a wide variety of applications in which it is desired to transfer heat between two fluids such as for example between a liquid flowing through the tubes and a gas directed across the fins thereof. In order to insure sufficient heat dissipation or transfer to the gaseous fluid flowing across the fins, it is often desirable to cause the fluid to make several passes through the finned tubes rather than a single pass. Such techniques may be employed for various reasons, one being to enable the heat exchanger to be contained within a relatively small envelope or overall size while still providing a sufficient heat dissipation for the intended use. These heat exchangers are generally referred to as multiple pass counterflow types.
In a typical construction of a multiple pass counterflow fin and tube heat exchanger a plurality of fluid conducting conduits are provided generally arranged in multiple rows, each conduit being surrounded by a plurality of substantially parallel spaced fins along its length. An inlet header is connected in fluid communication to one end of each of a series of fluid conduits defining a first row and an outlet header similarly connected to one end of another row of fluid conduits. Assuming for example the heat exchanger is a two pass counterflow type having only two rows of fluid conduits, the other ends of the first and second row must be interconnected so as to conduct the fluid from the inlet header to the outlet header. One manner which has been employed for interconnecting these fluid conduits is by providing a separate return bend assembly for each pair of conduits. Such a construction is disclosed in U.S. Pat. No. 3,420,692. While this type of return bend construction is effective in interconnecting the separate conduits, it is relatively expensive to manufacture and assemble requiring each return bend assembly to be separately manufactured and assembled to the heat exchanger core. Further, in order to protect the return bend members as well as to provide a frame for the heat exchanger such as to provide attachment points for securing the heat exchanger to equipment with which it is to be used, a separate frame member must be fabricated and assembled thereto.
Accordingly, the present invention provides an improved return bend construction which provides a single return bend assembly which may be assembled as a single unit to one end of the heat exchanger core so as to place each fluid conduit in one or more rows in direct fluid communication with the corresponding fluid conduit in an adjacent row or rows. The return bend assembly of the present invention requires the assembly of only two separately fabricated pieces which are operative to interconnect all of the fluid conduits provided at one end of the heat exchanger core in any desired configuration. Thus, substantial cost savings may be realized both in the manufacturing of the return bend assembly as well as in the assembling of the complete heat exchanger. Further, the base member of the return bend assembly of the present invention may be designed to function as a portion of the heat exchanger frame as well as include mounting means for securing the heat exchanger to the equipment with which it is to be used. Also, the return bend assembly of the present invention provides a substantial mutually engaging surface area surrounding each of the passageways provided between the two assembled pieces which greatly reduces the possibility of leaks being encountered during the life of the heat exchanger.
Additionally, the return bend construction of the present invention is well suited for a variety of heat exhanger designs including those in which each adjacent row of fluid conduits conducts fluid in an opposite direction as well as those in which several adjacent rows of fluid conduits conduct fluid in the same direction and groups of rows are interconnected to conduct fluid in opposite directions.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.